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<title>Machine Desc (GNU Compiler Collection (GCC) Internals)</title>

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<h2 class="chapter" id="Machine-Descriptions"><span>17 Machine Descriptions<a class="copiable-link" href="#Machine-Descriptions"> &para;</a></span></h2>
<a class="index-entry-id" id="index-machine-descriptions"></a>

<p>A machine description has two parts: a file of instruction patterns
(<samp class="file">.md</samp> file) and a C header file of macro definitions.
</p>
<p>The <samp class="file">.md</samp> file for a target machine contains a pattern for each
instruction that the target machine supports (or at least each instruction
that is worth telling the compiler about).  It may also contain comments.
A semicolon causes the rest of the line to be a comment, unless the semicolon
is inside a quoted string.
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<p>See the next chapter for information on the C header file.
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<li><a href="Overview.html" accesskey="1">Overview of How the Machine Description is Used</a></li>
<li><a href="Patterns.html" accesskey="2">Everything about Instruction Patterns</a></li>
<li><a href="Example.html" accesskey="3">Example of <code class="code">define_insn</code></a></li>
<li><a href="RTL-Template.html" accesskey="4">RTL Template</a></li>
<li><a href="Output-Template.html" accesskey="5">Output Templates and Operand Substitution</a></li>
<li><a href="Output-Statement.html" accesskey="6">C Statements for Assembler Output</a></li>
<li><a href="Predicates.html" accesskey="7">Predicates</a></li>
<li><a href="Constraints.html" accesskey="8">Operand Constraints</a></li>
<li><a href="Standard-Names.html" accesskey="9">Standard Pattern Names For Generation</a></li>
<li><a href="Pattern-Ordering.html">When the Order of Patterns Matters</a></li>
<li><a href="Dependent-Patterns.html">Interdependence of Patterns</a></li>
<li><a href="Jump-Patterns.html">Defining Jump Instruction Patterns</a></li>
<li><a href="Looping-Patterns.html">Defining Looping Instruction Patterns</a></li>
<li><a href="Insn-Canonicalizations.html">Canonicalization of Instructions</a></li>
<li><a href="Expander-Definitions.html">Defining RTL Sequences for Code Generation</a></li>
<li><a href="Insn-Splitting.html">Defining How to Split Instructions</a></li>
<li><a href="Including-Patterns.html">Including Patterns in Machine Descriptions.</a></li>
<li><a href="Peephole-Definitions.html">Machine-Specific Peephole Optimizers</a></li>
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